1. Field of the Invention
The present invention relates to improvements of a work/head positioning apparatus, a flux reservoir, a mount head and a transfer head to be respectively used in a ball mount apparatus for mounting solder balls, solder bumps, or the like, on a wafer or a substrate.
The present application is based on Japanese Patent Applications No. Hei. 11-172002, 11-177523, 11-177524, 11-186091 and 11-195690, which are incorporated herein by reference.
2. Description of the Related Art
A background-art solder ball mount apparatus had also a driving mechanism which could be used for positioning three axes such as X-, Y- and "THgr"-axes provided on the work side regardless of the existence of a driving mechanism which was provided in a mount head, a flux transfer head, or the like, for use for performing positioning. Provision of such a multi-axial driving mechanism however resulted in mechanical complexity and consequently in increasing factors of trouble.
Further, in a flip chip bonder, a ball mount apparatus, or the like, in the background art, an apparatus for transferring flux to a work was used. In such an apparatus, a bonding head which holds a work was moved down to a flux reservoir so that flux was transferred to the work, or a transfer head was moved down to a flux reservoir so that flux adhering to the transfer head was transferred again to a desired work.
In such a flux reservoir 10 (flux supply unit), the thickness of a flux layer 440 in a flux reserving space 14 is smoothed by a squeegee 15 in order to transfer uniform flux to a work or a transfer head 13. If the flux layer 440 is smoothed by the squeegee 15, flux protuberances 441 and 442 are produced at edge portions of the flux layer 440 as shown in FIGS. 23 and 24. There is less problem even if such protuberances 441 and 442 are produced in the case where flux is transferred all over the work. However, in the case where flux is transferred to the transfer head 13, there arises a danger of applying flux to unexpected portions of the transfer head 13 due to the protuberances 441 and 442 as shown in FIG. 24.
There occurs no serious problem in the case where a transfer head has large transferring protrusion portions as in the background art. However, such transferring protrusion portions have been reduced in size and increased in density with the recent development of very small chips. Accordingly, there is a possibility that a problem may occur. In order to avoid such a problem, it is possible to prevent flux from rising if the area smoothed by the squeegee is increased. In this case, however, the flux reservoir becomes large undesirably in the case where transferring is performed on a large area at a time, for example, so as to transfer flux to a wafer in a lump.
Still further, in a background-art solder ball mount apparatus, the position of a mount head or a flux transfer head was fixed, and the position of a work was adjusted to coincide with that of the head so as to position the head and the work. Therefore, there was no position recognizing means on the head side, and there was only means for recognizing the position of the work. However, with the recent tendency to make balls very small and mount a large quantity of balls in a lump, there was a jump in required positioning accuracy. As a result, the mount quality could not be ensured if the positions of the head and the work were recognized in such a background-art method.
Still further, in a mount head for sucking solder balls in a background-art solder ball mount apparatus, a large number of suction holes for sucking solder balls were provided in a vacuum plate disposed on the lower surface of the mount head. The mount head was decompressed by vacuum means so as to suck solder balls in the suction holes. Then, the mount head was moved above a work so as to mount the solder balls on the work.
When solder balls or the like were mounted on a work, it was essential to keep proper parallelism between the vacuum plate and the work in order to make the mount head mount solder balls or the like on the work accurately. Particularly when a large quantity of solder balls or the like were mounted on the work, it was important to ensure such parallelism. However, the vacuum plate was often distorted due to the tendency to make the vacuum plate thinner or other reasons, so that it was difficult to keep proper parallelism between the vacuum plate and the work.
Still further, in a background-art solder ball mount apparatus, there was a transfer head using a screen, that is, a transfer head in which a film-like (plate-like or sheet-like) screen provided with protrusions on its lower surface was strained with a tension, as a new system for transferring a very small amount of flux onto a wide area. In this system, however, there occurred such a phenomenon that a screen 238 was bent at its center portion when the transfer head was pressed onto a flux supply portion 16 as shown in FIG. 22. Accordingly, there was a problem that a difference appeared in flux adhering quantity between the center and the circumference of the transfer head.
Generally, a driving mechanism which could be used for positioning at least one axis for horizontal movement other than a lifting axis (Z-axis) was provided also in a mount head or the like also in a background-art solder ball mount apparatus. According to the present invention, paying attention to this fact, in order to solve the foregoing problem, it is a first object of the present invention to provide a solder ball mount apparatus in which a driving axis for driving a mount head or the like is used as a positioning driving axis so that excessive driving axes are reduced in the solder ball mount apparatus as a whole and a driving mechanism is made simple. As a result, factors of trouble are reduced.
It is a second object of the present invention to provide a flux reservoir and a flux transferring method in which flux does not adhere to any unexpected portion of a transfer head, so that transferring can be performed surely even if the flux reservoir is compact in size and transferring is very fine.
It is a third object of the present invention to provide a ball mount apparatus with a positioning apparatus and a positioning method. Positioning alignment marks are provided also on a head side, and both the positions of the head and work are recognized. The head and work are positioned on the basis of the results of the recognition. Thus, it is made possible to satisfy the high positioning accuracy required with the recent tendency to make balls very small and to mount a large quantity of balls in a lump.
It is a fourth object of the present invention to provide a mount head in a ball mount apparatus in which parallelism is ensured between a work and a vacuum plate so that a large quantity of solder balls can be mounted on the work accurately.
It is a fifth object of the present invention to provide a transfer head in which such a phenomenon that a screen is bent at its center portion is not produced even when the transfer head is pressed onto a flux supply portion, so that there does not appear a difference in flux adhering quantity between the center and the circumference of the transfer head, and the flux adhering quantity can be made uniform.
According to a first aspect of the present invention, there is provided a work and head positioning apparatus to be provided in a ball mount apparatus, the work and head positioning apparatus moving a work and a head relatively to each other to perform positioning of the head and the work, comprising:
a head driving mechanism for driving the head substantially in a linear direction;
a first work driving mechanism for driving the work, the first work driving mechanism extending in a direction intersecting the driving mechanism; and
a second work driving mechanism for driving the work in a rotational direction on the first work driving mechanism,
wherein the three driving mechanisms are driven so that a positional relationship between the work and the head is adjusted.
According to a second aspect of the present invention, there is provided a flux reservoir comprising:
a main body;
a flux reserving space provided on the main body, and the flux reserving space having a flat supply area for transferring flux to a transfer head; and
a squeegee for smoothing a flux provided in the flux reserving space so the flux is provided on at least a whole of the flat supply area,
wherein the flat supply area in the flux reserving space is made substantially as large as a transfer area of the transfer head, and is made movable up relatively to the flux reserving space except the flat supply area while keeping substantial parallelism between the flux provided on the flat supply area and the transfer area of the transfer head.
According to a third aspect of the present invention, there is provided a work and head positioning apparatus to be provided in a ball mount apparatus, comprising:
an alignment mark provided in a head;
first optically recognizing means for recognizing the alignment mark;
second optically recognizing means for recognizing a position of a work;
operation means for carrying out an operation for obtaining a quantity of a relative positional gap between the head and the work based on a recognition result of the first and second optically recognizing means; and
control means for giving movement instructions to a driving mechanism for driving respective axes of the head and the work based on a result of the operation means.
According to a fourth aspect of the present invention, there is provided a mount head to be used in a ball mount apparatus, comprising:
a main body;
a vacuum plate having a large number of suction holes for sucking balls and disposed on a lower portion of the main body;
a gas-conducting path forming member disposed in the main body and above the vacuum plate to support the vacuum plate against external force, the gas-conducting path forming member having gas conducting paths which do not correspond to the suction holes of the vacuum plate; and
a gas conducting permeable member disposed between the vacuum plate and the gas-conducting path forming member.
According to a fifth aspect of the present invention, there is provided a transfer head comprising:
a main body having a frame on a lower surface thereof;
a screen having transfer protrusions provided on a lower surface thereof, the screen being strained with a tension over the frame; and
urging means being disposed above the screen, the urging means giving no force to the screen in a no-load state but urging the screen downward when an upward load is given to the screen.